Cons:
Some schools look negatively at people who quit graduate programs, like Basil said.
Having to go through the entire application process again.
Pros:
It's better to realize that a PhD program is not for you early, then be miserable for the next 4-6 years.
There's a lot of information on the internet about how quitting a graduate program is a kiss of death in terms of your application. And this might be true for the top PhD programs, but I also know people who have quit one program and still got accepted at another. It really depends on the applicant and the circumstance I think.

Thought this was super interesting. This article talks about how biomedical informatics and machine learning is helping clinicians better diagnosis and treat schizophrenia. Here's an excerpt from the article:
Full link: http://www.medscape.com/viewarticle/883788

I think it would be nice to start a list of all the Ph.D Programs that accept MCAT Scores. I started this below.
Ph.D Programs that Accept MCAT Scores:
Ohio State's Biomedical Informatics Ph.D. Program
University of Iowa's Biomedical Sciences Program
Standford University's Biomedical Informatics Ph.D. Program
I will continue to add schools as I find them. Please post below if you know of a Ph.D. Program that accepts MCAT scores.
Masters Programs that Accept MCAT Scores:
Georgetown University Microbiology
Wake Forest

Nice response. I agree with this a lot. I would say that for people who are unsure of what exactly they want, a masters is a much better route. It gives you a good feeling of the academic side of things, while also allowing you to pursue internships and gain valuable skills that companies are interested in. Of course, everything is subjective, but I have seen this to be true for most cases.

For anybody here who is not in the Computer Science field, but something outside (Data, Biology, etc), and have used Machine Learning, how exactly did you implement it? What were you trying to achieve using Machine Learning? What programming languages or software did you incorporate?